KR100379604B1 - Structure of tundish for guaranteeing manufacture of clean steel during eccentric injection between ladle and tundish in continuous casting process - Google Patents

Abstract

PURPOSE: A structure of tundish is provided which reduces steel slab quality difference between both molds generated during injection of molten steel into eccentric position of tundish instead of center of tundish when injecting molten steel into tundish from ladle by changing structure of dams and weirs in tundish in the continuous casting process. CONSTITUTION: In a tundish(2) of the continuous casting process in which molten steel is cooled as molten steel is passing through molds(3) and second cooling section(6) after molten steel(4) in ladle(1) is injected into tundish through shroud nozzle(5), the structure of the tundish is characterized in that weirs(10) and dams(9) are sequentially positioned at a side of the tundish where a distance between the shroud nozzle and submerged entry nozzle is long, height of the dam is 0.25 to 0.31 H0, wherein the H0 is height of the surface level of molten steel, the dams and the weirs are positioned in order of dam, weir and dam again at a side of the tundish where a distance between the shroud nozzle and the submerged entry nozzle is short, and a residual molten steel discharge hole is formed a central lower part of the dam close to the submerged entry nozzle.

Description

Tundish structure to ensure clean steel manufacturing during ladle-teddy time eccentric injection of the playing process

In the continuous casting process consisting of a ladle-tundish-mould, the present invention is not the center of the tundish but the eccentricity of the tundish in the process of injecting molten steel from the ladle to the tundish by changing the structure of the dam and weir in the tundish. The present invention relates to a tundish structure for reducing the quality difference between the cast pieces generated when the molten steel is injected into the position.

In general, the slab caster is composed of a ladle (1)-tundish (2)-mold (3) as shown in FIG. The molten steel 4 in the ladle is injected into the tundish 2 through the shroud nozzle 5 and then distributed to both molds 3 and cooled by passing through the mold and the secondary cooling stand 6.

The tundish 2 of the continuous casting process distributes the molten steel 4 injected from the ladle 1 to both molds 3, relieves the static static pressure acting on the solidification layer (16 in FIG. 4) and the molten steel 4 ) To raise the inclusions toward the tap surface so that the inclusions react with the slag 8 of the tap surface to dissolve and absorb. Various types of dams 9 and weirs 10 are used to control the flow of the molten steel 4 in the tundish 2.

The dam is attached to the bottom of the tundish, and has a structure in which the molten steel passes through the upper portion thereof, and the wear is similar to the dam, but has a structure in which the molten steel passes through the bottom of the tundish and is cut off.

In general, as shown in FIG. 1A, the ladle 1 has two collector nozzles 11 and 12, one for injection and the other for emergency opening used when the nozzle cannot be opened.

During the continuous casting of the ladle (1) it was used for injection and emergency opening by alternating both nozzles for each heat (heat). Recently, however, as the nozzle opening rate of the ladle 1 is improved with the development of steelmaking technology, only one nozzle is used to simplify the ladle 1 repair and minimize the molten steel inlet of the tundish cover. Therefore, the molten steel injection position 13 in the tundish 2 is fixed so that the distance between the injection position and the tundish nozzle is closer to the X side and closer to the Y side in the drawing, regardless of the performance of the cast heat.

Previously, molten steel was injected alternately into the X and Y sides, but the quality variation between the molds (3) was not recognized, but the quality of the casts with the eccentric injection tended to be biased toward the X or Y side depending on the type of defect. As shown in Fig. 2, the occurrence rate of the X-side is high in the case of the surface inclusions of the cast steel, and Y-side in the case of the internal inclusions. When the problem of cast quality between the two molds (3), not only the quality non-uniformity problem in quality control but also the source of defects is concentrated on one side of the mold (3), causing a problem that the incidence of cast defects also increases.

Looking at the temperature and flow state of the molten steel in the tundish (2), in the case of the central injection of Figure 1b injected molten steel 4 passes between the weirs 10 through the dam (9) to each mold (3) on both sides Is injected. In this case, the temperature distribution and the flow velocity distribution of the molten steel 4 are in the same state on both sides. However, as the molten steel injection position 13 of the shroud nozzle 5 is eccentric, the temperature and flow rate distribution of the molten steel are asymmetric. Investigation of the molten steel temperature at the top of the immersion nozzle (14 in FIG. 4) in the tundish as shown in FIG. 3 shows that the molten steel temperature is higher in the Y side than in the X side. Numerical results also show similar trends. This is because the distance between the molten steel injection position 13 and the immersion nozzle 14 is far, so that the temperature drop of the molten steel 4 is greater.

When the temperature of the molten steel 4 decreases, as shown in FIG. 4, the casting solvent 14 facilitates the low temperature nozzle clogging in the immersion nozzle 14 to cause fluctuations in the mold surface, thereby allowing the mold solvent 15 to be easily applied to the solidified layer 16. Collected, the nozzle clogging material 17 and the like are also separated from the nozzle wall surface and collected in the solidification layer 16 to become the surface inclusions of the cast steel.

In order to investigate the residence time in the tundish of the molten steel flowing from the molten steel injection position of the tundish 2 to the two mold 3 side, a copper (Cu) component is introduced into a tracer to continuously collect the molten steel 4 in both molds. The molten steel residence time was investigated by investigating the change of copper component, and the result is shown in FIG. It was confirmed that the maximum stay time was shorter on the Y side than on the X side. Therefore, it can be seen that the Y side is less likely to separate the floating of the non-metallic inclusions, which is in good agreement with the fact that the Y side has a high incidence in the case of the internal inclusions in FIG. 2.

The present invention has been made to solve the above-described problems of the prior art, to minimize the quality deviation between the two molds caused by the eccentric injection of the molten steel of the ladle in the continuous casting process consisting of ladle-tundish-mould It is an object of the present invention to provide a tundish structure that guarantees clean steel production during ladle-teddy time eccentric injection of a performance process.

Figure 1a is a view showing the structure during eccentric injection in the schematic diagram between the ladle-tundish mold of the playing process.

Figure 1b is a view showing the structure at the center injection in the schematic diagram between the ladle-tundish-template of the playing process.

FIG. 2 is a diagram comparing cast defects between both molds of tundish during eccentric injection. FIG.

Figure 3 is a view showing the difference between the molten steel temperature between the two molds of the eccentric injection tundish.

4 is a schematic diagram of the defect formation in the cast steel.

5 is a view showing the actual molten steel residence time during eccentric injection.

Figure 6 shows the position of the tundish weir and dam.

7 is a view showing a characteristic configuration of the present invention.

Table 1 is a table showing the retention time ratio and the maximum residence time according to the position of the dam / ware according to the water model test according to an embodiment of the present invention.

Table 2 is a table showing the retention time ratio and the maximum residence time according to the position of the dam / ware / dam result of the water model test according to another embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

1: ladle 2: tundish

3: mold 4: molten steel

5: Shroud Nozzle 6: Second Cooling Table

7: molten steel 8: slack

9: dam 10: ewe

11, 12: Collector nozzle 13: molten steel injection position

14: immersion nozzle 15: molding solvent

16: solidification layer 17: nozzle clogging material

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

The present invention relates to a tundish structure for reducing slab quality between the two molds generated in the process of injecting molten steel from the ladle to the tundish by changing the structure of dams and weirs in the tundish during the playing process. .

The present invention relates to a tundish of a continuous casting process in which molten steel in a ladle is injected into a tundish through a shroud nozzle and then cooled while passing through a mold and a secondary cooling stand, wherein the tundish is formed between the shroud nozzle and the immersion nozzle. The far side is located from the shroud nozzle in the order of weir and dam, and the height of the dam is 0.25-0.31Ho (where Ho is the height of the floor), and the shroud nozzle and the immersion nozzle The distance between them is located in the order of dam, weir, and dam from the shroud nozzle, and the ladle-teddy of the playing process, characterized in that it has a hole for discharging the residual water in the lower center of the dam close to the immersion nozzle. It relates to a tundish structure which guarantees clean steel production during time eccentric injection.

At this time, the height of the dam is limited to 0.25-0.31Ho, when the height of the dam is less than 0.25Ho or higher than 0.31 Ho, the maximum residence time is shortened with decreasing the molten steel residence time in the tundish, thereby removing the adverbs of inclusions. This is because the ability is degraded.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example 1)

Table 1 below shows the retention time ratio and maximum residence time between the two molds while changing the position of the dam and weir under the existing tundish dam and weir conditions.

A residence time ratio of both X and Y sides was obtained by inserting a potassium chloride (KCI) tracer into the shroud nozzle of several models and examining the tracer concentration through an conductivity meter at the immersion nozzle. The maximum stay time of Y side / maximum stay time of X side) and the maximum stay time of both sides were considered as the maximum stay time. Here, Ho is the hot water level, as shown in Figure 6, Lo is the distance between the X-side tundish nozzle and Y-side tundish nozzle.

In the case of the existing case, as shown in the far left of the chart, the residence time ratio is 0.675, and the residence time on the X side is long, which is in good agreement with the above results. The dam and weir on the Y side were moved to increase the residence time on the Y side. As the Y-side dam was moved, the residence time ratio increased, approaching the level 1 at 0.82-0.79Lo. As a result of moving the Y side weir, the deviation of the residence time ratio on both sides resulted in an increase. On the contrary, the X-side stay time was shortened by moving the dam on the X side to the immersion nozzle side, and this time approached the 1 level when 0.08Lo-0.06Lo. In the case of Table 1, the maximum residence time in all cases was below 1.11, which was lower than the existing conditions.

TABLE 1

* Dam and weir are top and bottom height respectively

* Stay time ratio = Maximum stay time on Y side / Maximum stay time on X side

* Maximum stay time = Maximum stay time on X or Y side / nominal stay time

(Example 2)

Table 2 below shows the height of the dam on the X side by installing the lower dam, and then installing the lower dam, and finally the lower dam in order to increase the molten steel residence time on the Y side in the water model of Example 1 The test was carried out by moving the position and the hole and drilling a residue discharge hole (not shown) in the lower dam on the Y side. In this case, the maximum residence time is higher than that of Example 1, and it can be seen that the floating removal ability of the inclusion is much superior.

TABLE 2

* Stay time ratio = Maximum stay time on Y side / Maximum stay time on X side

* Maximum stay time = Maximum stay time on X or Y side / nominal stay time

When the height of the X-side dam was changed from 0.23Ho to 0.34Ho, the residence time ratio approached 1 and the residence time was maintained to be 1,2 between 0.25-0.31Ho. On the other hand, as the position of the dam increases from 0.05Lo to 0.25Lo at 0.23Ho, the residence time ratio decreases from 1.4 to 0.9, and the residence time ratio approaches 1 at 0.20-0.25Lo, but in this case, the molten steel flows out between the dam and weir. It is not practical because there is no room for it.

Finally, the drain hole was drilled in the lower part of the dam to minimize the residual molten steel when tungsten was excluded. For the dam on the X side, the molten steel discharge time is defined in the case where the receptacle outlet is drilled in the center bottom and both discharge holes in the Y-side dams, the hole is drilled in the first dam and the hole is drilled in the second dam. Investigated. As a result, the case of the second dam was drilled, which satisfies the residence time ratio 1 and the longest stay time, which was most advantageous for the separation of the inclusions.

In summary, as shown in FIG. 7, when molten steel is injected into an eccentric position other than the center of the tundish in the process of injecting molten steel from the ladle to the tundish in a continuous casting process consisting of a ladle-tundish-mould. In order to minimize the quality difference between the two casting molds, the tundish is located at the far side between the shroud nozzle and the immersion nozzle in order from the shroud nozzle to the weir and the dam, and the height of the dam is 0.25-0.3Ho. The distance between the shroud nozzle and the immersion nozzle is closer to each other in order from the shroud nozzle to the dam, the ware, and the dam, and has a hole for discharging the residue in the center lower portion of the dam close to the immersion nozzle. You can see what you can do.

The present invention can maximize the separation time of molten steel inclusions in tundish by minimizing the variation of the dwell time in molten steel and maximizing the dwell time, as well as modifying the structure of dams and weirs in tundish in the continuous casting process. Through the injection of molten steel from the ladle to the tundish, there is an effect of reducing the quality difference between the two casts generated when the molten steel is injected into the eccentric position rather than the center of the tundish.

Claims (1)

In the tundish of the continuous casting process in which molten steel in the ladle is injected into the tundish through the shroud nozzle and then cooled through the mold and the secondary cooling stand, The tundish is located at the far side between the shroud nozzle and the immersion nozzle in the order of the weir and the dam from the shroud nozzle, and the height of the dam is 0.25-0.31Ho (where Ho is the height of the floor) The distance between the shroud nozzle and the immersion nozzle is closer to each other in order from the shroud nozzle to the dam, the ware, and the dam, and a hole for discharging the residual water in the center lower portion of the dam close to the immersion nozzle. A tundish structure to ensure clean steel production during ladle-teddy time eccentric injection of the playing process, characterized in that it has a.